A Permanent Virtual Circuit is a logical data channel on a physical transmission medium, which is running on an ATM protocol stack. A PVC in an ATM network is uniquely identified by the combination of three attributes: 1) a port number, 2) a virtual path identifier (VPI), which is an 8-bit field; and 3) a virtual channel identifier (VCI), which is a 16-bit field. Whereas the port number associated with a PVC has a physical correspondence to the transmission medium (e.g., the specific T1 line among a group of T1 transmission lines that is selected to terminate the PVC), the VPI and VCI used to identify the PVC are logical designations and have no physical correspondence.
In the prior art, each end point of a PVC is provisioned by selecting a VPI and a VCI together with the port number on the physical medium on which the end point terminates. PVCs on an ATM network are used in many different type of network applications. For example, in an exemplary service provider's wireless network shown in FIG. 1, an ATM network 101 serves as the backhaul network interconnecting the Base Station Controllers (BSCs) 102-1-102-N that are supported by a Mobile Switching Center (MSC) 103. MSC 103 is connected to each BSC 102 via a T1 and Ethernet connection 110. Other MSCs, not shown, will are connected to other BSCs, which in turn are connected through the same or through another ATM network to other BTSs. Each BSC 102 connected to MSC 103 is associated with and controls one or more Base Transceiver Stations (BTSs) 104-1-104-M and each BTS is uniquely associated with and is controlled by one of the BSCs. A mobile station 105 subscribing to this provider's wireless services that is communicating with another mobile station on this wireless network or another wireless network or with a station 111 connected to the wire-line Public Switched Telephone Network (PSTN) 112, communicates over an air interface with one of the BTSs 104-1-104-M.
The ATM network 101 includes an ATM edge switch 106 to which the BSCs 102 and MSC 103 are connected and an ATM edge switch 107 to which the BTSs 104 are connected. In this exemplary network, each of the BSCs 102 are connected to switch 106 via between 1 and 8 T1 lines 108, MSC 103 is connected to switch 106 via an OC-3 carrier 113, and each of the BTSs 104 are connected to switch 107 via between 1 and 4 T1 lines 109. Signaling traffic, such as call setup, etc., between a BSC 102 and one of its associated BTSs 104 is carried over a PVC. A PVC which carries signaling traffic is referred to herein as a “signaling PVC.” For fault tolerance and redundancy purposes there generally will be two signaling PVCs between each BTS 104 and its associated BSC, a primary signaling link and an alternate signaling link each carried on a separate T1 line. Bearer traffic, such as voice or data call traffic is carried on a PVC between a BTS 104 and MSC 103, and is associated with a particular one of the BSCs 102. A PVC which carries bearer traffic (voice or data) is referred to herein as a “bearer PVC,” also known a ATM Packet Pipe. For this exemplary network, there are up to 12 bearer PVCs between a BTS 104 and MSC 103 that are associated with a particular BSC 102. Each BTS 104 can thus terminate up to 14 PVCs: 2 signaling PVCs and 12 bearer PVCs. These 14 PVCs, numbered from 1 to 14, are provisioned at their BTS-end over the T1 lines 109 connecting their associated BTS with ATM edge switch 107. At the MSC/BSC-end of the PVC, the signaling PVCs among these 14 PVCs, numbered 1 and 2, are provisioned between ATM-edge switch 106 and the associated BSC 102 over T1 lines 108. The 12 bearer PVCs, numbered 3-14, are provisioned between switch 106 and MSC 103 over an OC-3 transmission line 113.
In the prior art, when provisioning either a bearer PVC or a signaling PVC, the service provider arbitrarily selects a VPI and a VCI at each endpoint of each hop of the end-to-end PVC, as well as selects a port number at each endpoint and quality-of-service (QOS) parameters. Generally, the VPI, an 8-bit number, is randomly selected in the range of 0-255, while the VCI, a 16-bit number, is randomly selected in the range of 32-65,535, with 0-31 being reserved by the ATM standards for other purposes. For example, in provisioning a first endpoint of a first hop at BSC 102-1 in a signaling PVC between BSC 102-1 and BTS 104-1, a VPI and VCI are randomly selected for the particular port of BSC 102-1 to which the T1 line that will carry that PVC is connected. Thus, for example, if this PVC will be carried on the T1 line connected to port 1 of BSC 102-1, and VPI=1 and VCI=100 are arbitrarily selected, the endpoint at BSC 102-1 of this PVC, represented by the triplet (VPI, VCI, Port#), is for this example (1,100,1). At the switch side, if that same T1 line is plugged into port 4 of switch 106, then the triplet (1,100,4) represents the switch-side endpoint of that first hop between BSC 102-1 and switch 106, where the VPI and VCI are maintained at the values they have at the BSC-end of the hop. At the other side of the ATM network 101, each end of the hop between edge switch 107 and BTS 104-1 is similarly provisioned. For this hop, the VPI and VCI pair can be selected to be the same or different than the VPI and VCI pair used on the hop between BSC 102-1 and switch 106. For example, this hop of the PVC can be provisioned on the T1 line connected to port 1 of switch 107 with a VPI=2and VCI=100, with the endpoint thus represented as (2,100,1). That T1 line could be connected to port 2 of BTS 104-1, so that the endpoint of that hop at BTS 104-1 is represented by (2,100,2). Once all the endpoints are provisioned, the ATM switch 101 is provisioned to map the endpoint (1,100,4) of the first hop at the BSC side of the switch to the endpoint (2,100,1) at the second hop at the BTS side of the switch in order to ensure end-to-end connectivity of that signaling PVC between BSC 101-1 and BTS 104-1.
Since there are multiple signaling and bearer PVCs connected between each BTS and its associated BSC/MSC, the service provider must separately provision each. With the VPI and VCI values of each hop of each PVC being arbitrarily selected, the service provider needs to accurately record and maintain the VPI, VCI and port numbers of each endpoint for each hop of each PVC in some type of spreadsheet or database lookup table. As a provider's network grows with more base stations being added to increase the provider's coverage area to meet growing demand, thousands of PVCs could easily traverse the provider's ATM backhaul network. Provisioning, managing and maintaining these multitudinous PVCs poses a formidable challenge. Troubleshooting an end-to-end PVC connection through each of its hops is particularly difficult when the endpoints of each hop need be separately identified and traced as the PVC is linked from hop-to-hop.